Back-barrier-induced fast transient trapping and threshold voltage instability in AlGaN/AlN/GaN HEMTs

Fast transient charge trapping in AlGaN/AlN/GaN high-electron-mobility transistors (HEMTs) was investigated using fast pulsed measurements. Two devices—with and without an Al0.08Ga0.92N back-barrier—were compared to evaluate the threshold voltage (Vt) instability under single-pulse stress from 1 ms to 1 s. The back-barrier device exhibited a slightly larger short-term Vt shift (<1 s) due to enhanced shallow-trap activation, while deep-trap charging was effectively suppressed, resulting in improved long-term stability. These results demonstrate that the AlGaN back-barrier enhances electron confinement and provides a physical pathway to mitigate long-term reliability degradation, clarifying the trade-off between fast transient trapping and deep-trap suppression in GaN HEMTs.